CPM 440V: any special sharpening tricks?

Rev. Pete

Rev. Pete

Joined
Aug 25, 2001
Messages
843
I've been working with a Spyderco Native marked "CPM 440V". I am having some trouble using my regular sharpening technique on this blade. I use a Sypderco Sharpmaker 204. Usually I sharpen on one side until I can feel the "wire edge" with my thumbnail. Then I sharpen the other side, move to the next finer stone, etc. I have been unable to get a wire edge on this CPM 440V blade. Is this steel so hard that it doesn't make an edge? It also seems like the blade is quite thick near the edge. I believe I am reaching the edge since I used the magic marker techique to check. After several sessions of trying to sharpen this blade to no avail (would not even cut paper) I finally had some limited success by just counting strokes on each side of the blade, starting with the diamond-coated stones and working down to the fine stone. At least now the edge will grab my thumbnail. It is still not sharp. I sincerely appreciate your tips and advice.
 
I've had more trouble sharpening the 440V on my Military, than other steel. You won't see me buying any more 440V.

I always had problems with 440V on my SharpMaker, and never got that scary sharp kind of edge. I finally got a good edge out of desperation when I chipped it out badly. I stropped the knife on 600 grit wet/dry paper. The sandpaper quickly removed the chips and put a fantastic working edge on the knife.
 
Use a diamond hone. This will let you thin your edge and will cut the vanadium carbides in the 440V alloy. The ceramic rods tend to push the carbides around. Do not strop when you are done. This seems counter productive on this alloy. I don't recall whether I got a perceptable burr when I sharpened my 440V blade. The alloy may be less ductile and produce less of a burr. Be sure to do a few super-elevated strokes near the end of your honing to remove any microburr you may have formed. This alloy will take a very sharp edge.

I used a medium-coarse diamond hone to thin my edge and then refined the edge using an extra fine diamond hone. Then I super-elevated my honing angle to about 35-degrees per side and alternated sides to remove the burr. Then I went back down to about 17-degrees to finish the edge. I might have given it a couple strokes per side with an extra-fine ceramic rod to smooth the edge at about 19-degrees.
 
It takes a lot of work to get a shaving sharp edge with CPM 440V. I have posted at some length on how to do this on the Spyderco section of this forum. If a general utility edge is required, step 3 of the Spyderco Sharpmaker gives an easy edge to create, whilst still very sharp.

I tend to rough the edge up every2-3 sharpenings with a fine diamond DMT stone, then I use step 4 of the Sharpmaker (Clean the crock sticks 1st) to get a nice edge. Shaving arm hair one way and then the other will tell you if you have a perfect geometric edge. Then I use the Ultra Fine Spyderco Benchstone to polish and finish with a slack belt strop to get a hair grabbin scary edge. This all takes about 15 mins work from start to finish. Easy when you know how.;)
 
I have an avalanche with cpm 440v and I use a lansky crock stick works quite well!!! :)
 
Ditto on the diamond hones. They work, they work fast and
do a good job. I use a Lansky system and am pleased with it.
Polishing the edge is not a good idea.
I have a number of knives in the CPM steels and I like them
very much. I like the edge holding qualities. After you get
over the hump of sharpining I think you will too.
 
Originally posted by Colinz
Patience.

/Colinz
Click to expand...
You can say that again!
BTW Colinz, is your avatar a scene in A Clockwork Orange?
 
spyderco 440v shouldn't be too hard to sharpen they leave the rc pretty low so that it won't be hard to sharpen in the first place
 
The thing that makes 440V hard to sharpen isn't so much the hardness as the abrasion resistance.

Compare 52100 at 60 Rockwell to 440V at 55 Rockwell and see what I mean.
 
manji> it's rc value is low to fix the chipping they had early on.

I have been enjoying my 440V CE Millie for 2 months now. I let the edge get "dull" once, and took me close to an hour to get back. Last time I just got below shaving and took about 15minutes total.

best tip: don't let it get dull.
 
I'm glad to see such positive effort in sharpening S60V! :D I keep hearing a lot of bad talk about S60V and S90V when it comes to sharpening. It seems these such users cannot work the material properly and label it as "not being able to take an edge as well" as other less "loaded" steels. Its irritating, especially since S90V is the only stainless I use.

Know the material, know your sharpening materials/tools and practice, practice, practice and you will get the results as you guys are. :cool: Makes my day. Bravo. he he

-Jason
 
The number one tool for solving sharpening problems is some kind of magnifier which will allow you to examine the edge, even 10x will do fine. If the edge isn't damaged, just dulled, then you should be able to restore it in less than a minute regardless of the steel. Yes some of the higher wear resistant alloys are hard to machine, but when sharpening such a knife you are talking about having to remove material that is on the order of 1/100", this is cut away very quickly on a modern quality hone.

To be clear, when I run edge retention trials I usually let the blades performance drop down to 5% or less than optimal. This is a very dull blade, it will also be restored with 5-10 passes on a v-rod set up, that is all. If the edge does not come back this fast then either you are not sharpening the edge but the shoulder or the edge is heavily damaged. As an aside, if it is the first time sharpening there could be a host of other problems because factory edges are often very uneven. Expect high and low points and variance in the angle. Unless you get all of this removed, you have a decent amount of stock removal ahead of you and this can indeed take some time but only has to be done once.

The best method when first sharpening a production blade (this should not be an issue with custom blades) with such a high abrasion resistance is to use reprofiling equipment to set the bevel below what you indend to sharpen. For example if you want to use the Sharpmaker at 15 degrees put 12-13 degree bevels on the blade. Now when you touch up the blade you are only hitting a very small strip of steel along the edge. This will speed the process up many times to one.

If you don't have access something when can do heavy stock removal fast (see a recent thread for details) then the best method is to use the 22 degree setting to sharpen (assuming the bevels are 15 which Spyderco ususally uses), and then when you have 10-15 minutes the next time the knife goes dull grind with the 15 degree coarse hones to put in the shoulder, no need to go any finer. You only need to do this when the 22 degree bevel that you are applying becomes large say a mm+ or so wide.

-Cliff
 
Cliff,

Do you have a suggestion on a type (or types) of a magnifier to use? I only have a cheapo 6x round magnifying glass and it just doesn't cut it.

Thanks,
--SAK
 
Radio Shack sells hand held magnifiers which work well, they are only 10x magnification but this allows you to see down to about 10 microns which is fine. If you have the money a quality stereo microscope would be best, but they are not cheap. However even a cheap regular microscope is of benefit and you can often find these for really cheap as they can be made out of plastics for kids, but they still function fine.

-Cliff
 
The only problem I've had with sharpening Spyderco's 440V is that it seems to quickly form a small burr which can be difficult to remove; when you try to grind it off, sometimes it just flips over to the other side of the edge. I don't know why it does that. Maybe it's because the steel is high alloy, yet it's heat treated to be relatively soft.

It's not a big deal though. If I increase the sharpening angle, use a stone that's not too fine, and use light strokes, then I can remove the burr without a lot of fuss.

If it's taking hours to sharpen, or you're not getting a burr, then sharpening technique is probably more likely to be the problem, rather than the steel.
 
Personally, I am not a fan of 440V. I have never been able to get any of my 440V Military folders scary sharp. Now, the ATS34 Military I currently own does take and hold an obscenely scary sharp edge!
 
I tend to stay away from 440V(S90V) for the simple reason that S30V has almost the same edge retention and it 4 or 5 times easyer to sharpen, i dont see the need to fight with S90V when S30V will act almost as well and cut my sharpening time from hours to 5-10 min.
 
cerulean :

[persistent burr]

Maybe it's because the steel is high alloy, yet it's heat treated to be relatively soft.
Click to expand...

Yes, the steel is pushed aroung easily by the hone because it is weak, and yet resists being cleanly cut becuase of the high alloy content. It is the worse combination of properties for achieving a high sharpness. For such high alloy steels you want to run them very hard to increase ease of sharpening as this will prevent large floppy burrs.

-Cliff
 
Originally posted by SAK
Cliff,

Do you have a suggestion on a type (or types) of a magnifier to use? I only have a cheapo 6x round magnifying glass and it just doesn't cut it.
Click to expand...

You can buy Jewlers loupes (small magnifyers for examining gemstones)
on ebay for up to 30x magnification.
 
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